1. Field of the Invention
The present invention relates to a device and method for displaying images, and more particularly, to a method of compensating image signals to improve display quality and a display device employing the method.
2. Description of the Related Art
Devices displaying images using liquid crystal generally have a liquid crystal layer with dielectric anisotropy between substrates of a display panel assembly. The liquid crystal display (LCD) devices display images by controlling the amount of light transmitting the liquid crystal layer. Such control of the amount of light is performed by controlling the intensity of electric field applied to the liquid crystal layer.
The liquid crystal display devices are flat panel display type and have thin film transistors as switching elements in pixels of the display panel assembly. Such TFT-LCD devices are widely used in image display systems and apparatus. A TFT-LCD device generally includes pixels, gate lines, and data lines. The TFT-LCD device also includes a gate driver, a data driver, and a timing controller. The gate driver applies certain voltages to the gate lines for turning on the switching element, and the data driver applies data voltages to the data lines for displaying desired images.
The conventional TFT-LCD devices have a relatively slow response rate of the liquid crystal and thus have some drawbacks in displaying moving images due to the slow response rate. Since the liquid crystal has a slow response rate in the conventional TFT-LCD devices, it takes time for the voltage level of a liquid crystal capacitance to reach a target voltage level, which is a voltage level necessary to gain a desired luminance. The time for reaching a target voltage level varies depending on a previous voltage level of the liquid crystal capacitance. In case that the difference between the previous voltage level and the target voltage level of the liquid crystal capacitance is excessively large, the voltage level of the liquid crystal capacitance is not able to reach the target voltage level during the switching elements are turned on.
There have been developments to improve the response rate of liquid crystal. One of the developments is a dynamic capacitance compensation (DCC) system, which utilizes the theory that the speed of charging electricity increases as a voltage level of the liquid crystal capacitance becomes larger. In the DCC system, a data voltage level (here, assuming that a common voltage level is zero) applied to a corresponding pixel is set to be higher than the target voltage level, so that the time for a voltage level of the liquid crystal capacitance to reach the target voltage level is reduced.
In the conventional DCC system, a signal to compensate image signals to be displayed is generated based on previous and present image signals. In the LCD devices employing the conventional DCC system, however, there have been problems such that the response rate of liquid crystal is relatively low in some gray scale changes (e.g., from black to white).
Therefore, a need exists for a system which compensates image signals while improving the response rate of liquid crystal. Further, it will be advantageous to provide an LCD device employing such a system of compensating image signals.